1. Field of the Invention
The present invention relates to an exposure apparatus used in a photolithography process for manufacturing a device, such as a semiconductor integrated circuit, a liquid crystal display device, or the like.
2. Description of the Related Art
When processing process wafers with a semiconductor exposure apparatus, the wafers carried in from the outside by an open cassette elevator or a coater developer are conveyed by conveying units and are brought to a wafer stage by a wafer loading hand. At this time, due to vibration of the apparatus generated when the wafer loading hand passes the wafers to the wafer stage or due to the shape or machining condition of the process wafers, a wafer chuck may suck the wafers on the wafer stage with a deviation exceeding the tolerance, causing a wafer vacuum error on the holding surface of the chuck.
In a known art, in such a case, the apparatus cannot accurately identify the amount of deviation, and, if the apparatus is driven, the wafers and the apparatus may be damaged. Thus, the wafers are recovered manually. Japanese Patent Laid-Open No. 11-124230 discloses that a positioning pin is installed on a conveying arm, and, upon the occurrence of a conveyance error of a substrate, the substrate is pressed against the positioning pin and is aligned with a predetermined position so that the deviated substrate is returned to a state capable of being automatically conveyed.
However, as in the above-mentioned known art, in order to recover the wafers manually, an operator has to touch the wafers through the spaces between the other units in the apparatus, making the manual recovery troublesome. Furthermore, the recovery of the wafers in the exposure apparatus disturbs the environment in the air-conditioned apparatus, and the operator may bring particles in the apparatus.